Lichens have long served as bioindicators as well as biological means of accumulating toxins from the environment, such as heavy metals and photoxidants. We have determined by means of light and electron microscopy that the medulla region of the lichen, Cetrari a cucullata is significantly affected by exposure to enhanced atmospheric sulfur and metal pollutants associated with nickel-copper smelting. We have furthermore determined the presence of a wide variety of pollutant elements within the lichen thallus which have the potential of eliciting free radical formation. EPR is an essential tool for better making the assessments of the state between samples from heavily polluted regions (northern Siberia) and presumed non-polluted areas (far NE Taimyr Penninsula).